The present invention relates to a method of producing electric circuit patterns.
Printed boards have been broadly used for carrying electric circuit patterns, on which are mounted, in electric contact therewith, electric devices such as IC chips, transistors, resistances, capacitances, inductances and so forth. For example, in case of the driving circuits of liquid crystal devices, IC chips are mounted on a printed board and electrically connected at their terminals (pins or contacts) with a number of addressing lines formed on the printed board. However, since a number of IC chips or other electric devices are connected with same electrode lines, the connection condition and the device performance of a respective device connected to common lines can not be tested independently.
An example of the connection of a prior art pattern with a device is schematically illustrated in FIGS. 1(A) to 1(C). A number of parallel buslines 15 are formed on a printed circuit board 1 by wet etching as shown in FIG. 1(A). A certain surface portion of the board is converted with an insulating film 4 over the buslines 15. In the insulating film 4, a number of apertures are opened in order to provide accesses to the buslines 15 as seen from FIG. 1(B). Furthermore, a number of local electrode lead lines 17 are formed in order to make electric contact with the buslines 15 independently through the respective apertures. One or several devices can be electrically connected with the bus lines 15 through the lead lines 17. This type of connection may be made in the same manner along the buslines 15. There are two problems in this prior art. One is disconnection between the lines 15 and 17 which may occur due to misalignment of the lines 15 and 17 and the apertures 16. This is likely particularly when the number of buslines to be coupled is increased. The other problem is the impossibility of independently testing of the connection between the device and the lines 15 and the test of the device performance as already pointed out supra.